This invention relates to a process for obtaining gas samples from a sealed glass ampule of the type commonly used in the medical field.
Glass ampules are commonly used in the medical field for preserving medicines of various types in a sealed environment for storage prior to use. At the time of use the ampules are broken at a scored groove in the neck of the glass, and a needle is inserted into the opening so that the medicine may be withdrawn with a syringe. At the time the ampule is prepared for manufacture the ampule has an open glass neck into which a measured amount of a desired liquid medicine may be inserted, and then the open neck of the ampule is heated to the melting point of the glass to cause the neck to form a glass seal, and to therefore enclose the medicine in the sealed glass ampule container. The filling process never completely fills the ampule, always leaving a small volume of gas in the container with the sealed liquid. For this reason, the filling process is completed in an inert gas atmosphere in order to ensure that the medicine will not become contaminated during storage from exposure to oxygen or other contaminating gases; the inert gas most frequently used is nitrogen.
There is a need to provide a quality inspection procedure for the manufacturing process described above, to sample the gas entrapped in the sealed ampule in order to verify that the gas does not contain any substantial quantity of oxygen, in order to confirm that the medicine in the ampule will have an adequate shelf life before use. Unfortunately, because the ampules comprise a sealed glass container, the quality inspection procedure requires that the ampule be broken in order to gain access to the gas contained in the interior, thereby creating a destructive testing process. This means that quality testing can only be done on a sampling basis, wherein random or statistically accurate samples of ampules are withdrawn from the assembly line process for testing. Further, even if a destructive process is used, it is extremely difficult to withdraw a gas sample from the ampule without contaminating the sample.